Electron beam deflection control system



Oct. 29, 1957 J. T.MCNANEY ELECTRON BEAM DEFLECTION CONTROL SYSTEM FiledMay 29, 1956 4 Sheets-Sheet 1 v INVENToR v JOSEPH {MCA/MEX 'TTORJVEX J.T. MCNANEY ELECTRON BEAM DEFLECTION CONTROL SYSTEM Oct. 29, 1957 FiledMay 29, 1956 v 4 Sheets-Sheet 2 INVENTOIL BY Y ZZ TTORNEY Oct. 29, 1957J. T. MCNANEY 2,811,668

ELEcTRoN BEAM DEFLECTION CONTROL SYSTEM Filed May 29, 1956 4 SheetsSheet3 a- H Z Munn.

nun-u" ,Wuuuuu Y INVENToA Joss/2H TMC/MNE! FIG; 7

Y ATTORNEY Oct. 29, 1957 J. T. MCNANEY ELECTRON BEAM DEFLECTION CONTROLSYSTEM 4 Sheets-Sheet 4 Filed May 29, 1956 a Elv @35 III El mfll Emmmmmmmm mmmmmm'nm IIIICI EICIIIIIIIIE] EEIEUE QIIIEIIIIISELv mmmmmmmmZVmmmmljmmm v INVENTOILA Y Josep/4 [MCA/AMEV BY ATTORNEY FIE 8 itd:States Patent claims; (Cl. 315-17) This invention relates generally tocathode ray tubesY and more particularly relates to an electrostaticdeflection system for deflecting electron beams in the cathode ray tube.

The deection systemutilizes cascade deflectionof the4 beam whichcombines the desirable effects of coplanar-like beam deilection withbeam angle deection control.

In my Vcopending application, Serial No. 414,551, now U. S. Patent No.2,761,988, issued September 4, 1956, I disclose a cathode ray apparatusfor selecting and displaying letters and numerals on a viewing screenforhigh speed recording purposes. The cathode ray apparatus disclosed inthat application employs a thin solid member in the path of an electronbeam in which a plurality of apertures are provided `for changing thecross-sectional shape -ot the electron beam into a'plurality ofcharacter contig-y urations. Deection platesare located between thesolid member of character-shaped apertures anda second solid member.containing an aperture. These deflection plates etfectselection ofindividual beams, from the plurality of` character .shaped beams,through the selecting aperture. Additional deflection plates areprovided for directing the :selected beam toward any part'of .theviewing screen of tthe tube. I have foundthat in this application, aswelll .as others, precise and exact alignment of the beams, seilectedthrough the selecting aperture, with the normal axisV Aof the tube isdesirable for the purpose of achieving satisection system that willrespond in a non-linear manner to factory registration of the characterson the screen.V Coni 4ventional cascade plate deection structures do notprovide 'the desired axial alignment of the beams as .they passthrough the selecting aperature.

Through the present invention,` Ihave overcome these diiiiculties byproviding. a beamdeilection system whichl references, withaihigh degreeof accuracy, all o f the individually selected beams to the` normal axisof the tube,

prior to their placement on the viewing screen. i

In another copending application Serial No. 507,856 Va cathode rayapparatus was disclosed which utilizes still another character` shapedbeamselection and deilection method of displaying letters and numeralson the viewing screen of ,a cathode ray tube. The cathode ray apparatusdisclosed in this applicationemploys a thin solid member, located alongthe path of thebeam of electrons emanating from a gun source, havingformed therein a` plurality of character-shapedapertures. A rst set `ofdeflection plates is located between the electron gun andthe'solidmemberfor directing thel electron beam toward selectedindividual apertur'es'inthe ,solidvmemben When the electron beam passes through an aperture, itis shaped in the form of thev cross section thereof -and travels yin adirection away from the normal axis of the tube. The shaped beams,however,

are directedl into the iield of an electromagnetic.lensvvhichv returnsthe beams toward'the normal axis of the tube. A second set of deflectionplates is located' along the axis at a location where the beams crossthe axis,- which plates cause the individual beam to be deected tobecome coaxial vagain with the normal axis of thetube.` `A-third setofdeilection plates is provided to direct the beamstoyvard any-1desired- Positioned in one end of the container is an electron beardffice part of the viewing screen. As is readily appreciable, veryprecise beam alignment is an important requirement in this secondcathode ray apparatus also. For the purpose of obtaining properregistration of message characters on the display screen it'isessential, prior to the placement of the character shaped beams -on thescreen, that these beams be returned very accurately to the normal axisof the tube. Because of optical distortions experienced in connectionwith the use of electro-magnetic lenses, and also electrostatic lenses,it has not been possible to achieve completely the degree offbeamalignment required.

The present invention may additionally be employed in the second cathoderay apparatus to overcome the present diculties. f

In addition to the aforestated objectsiand advantages, it is an lobjectof this invention to compensate for the spherical `aberrations oftheelectron optical system of a cathode ray It is another object of thisinvention to provide an electrostatic. deflection system which produces,in eiect, coplanar-like deflection of an electron beam in both verticaland horizontal directions.

by either a magnetic lens or an electrostatic lens, the beams will crossVthe axis at a common point along the axis andto provide a second deecting means that will cooperate with the first means in returning thebeams to the normal axial path.

' I t is another object of this invention to provide a beam defletion`system which will provide for compensating of eitherpincushion orbarrel distortion effects of an electron beam convergence lens,

I t is another object of'tlhis invention to provide a delinearlygraduated deection control voltages.

Objects and advantages'other than those set forth will be apparent fromthe Vfollowing description when read in. connection with theaccompanying drawings, in which;

' Figure 1 is a schematic diagram of a portion of a cathode ray tubeembodying the invention and showing an electron optical system whichmakes use of a selecting aperture for the selection of a particular beamfrom a plurality of beams derived from a beam'forming matrix,embodyingthe invention;

Figure 2 is a schematic diagram of another embodimen utilizing theinvention in the selection of a particular beamy from a plurality ofcharacter shaped beams emitted from the surface of a thermionic cathodeand for target positioning; v

Figure 3 is a schematic diagram of another embodiment of the invention;

Figures 4a, 4b, 4c show in detail a construction of thedeilection'plates of the systems shown in Figures 1, 2 or 3;

Figures 5a, 5b and 5c show in detail another construction of thedeflection plates of the systems shown in Fig.- ures 1, 2 or 3;

Figures 6a, b and c, are diagrams showing the source K and correction ofnon-axial beam alignments;

Figure 7 is a diagram showing the source of spherical aberrations;

Figure 8 shows the eiects of spherical aberrations on registration;

vFigures 9a, b and c are diagrams showing the relationship of characterregistration between the image and the object of character formats inthe beam forming element.

Shown in Figure l is a cathode ray display tube utilizing an evacuatedenvelope or container 1 of the type de scribed in my copendingapplication Serial No. 414,551.

generating means including a cathode 2 and a control grid 4. Theelectron beam 9 generated is projected generally along an electrical orelectro-optical axis 39 of the tube toward a target 40, such as a wellknown phosphor screen or conductive plates or the like, positioned atthe other end of the envelope. Impingement of the cross-section of thbeam 9 on the target will cause the target or screen 40 to be excitedand change electron bombardment into a corresponding light image. Thetarget 40 may be of a construction common to each of the tubes as shownin Figures l, 2 or 3. l

A convergence means, which may be electromagnetic or electrostatic, isshown as an electrostatic lens 6. This lens 6 is positioned along thetube for focusing the beam cross-section to a predetermined location,which location will determine the plane of influence at which the beam 9will be deflected. A beam forming means or matrix 7, having therein aplurality of character shaped openings, is positioned in front of thelens and will impart at least one cross-sectional shape to the beam 9.4In the simplest embodiment it may be desirable to have the matrixpositioned intermediate the beam generating means and the target. l

Immediately in front of the matrix 7 isl positioned a beam deflectionsystem 8. Deflection system 8 Vis typical of the preferred embodiment ofthe invention. The system 8 in its simplest form may be disposedintermediate the beam generating means and the target of the tube 10. Adeflection system, in accordance with deflection system 8, may beemployed to deflect the electron beam 9 in various applications: suchas, in Figure l, system 8 will deflect the beam 9 to position a portionof the beam through aperture 12 in aperture plate 11; system 16positions or directs different shaped cross-sections of the beam todesired positions on the target; in Figure 2, system 28 performs a likefunction as system 8; in Figure 3, system 28 performs =a functionsimilar to system 8 (Figures l and 2) wherein the electron beam ispositioned to illuminate at least a desired part of matrix 20; systems29, 30 -fof like construction with system 8 performing, respectively, areferencing function and a target positioning function upon the beam.The referencing function is disclosed more fully in the copendingapplication of Omer F. Hamann, Serial No. 507,902, assigned to thecommon assignee hereof.

Reverting to the operation of Figure l, the action of the lens 6 causesa beam of electrons 9, emanating from the cathode 2, to cross-over at apredetermined location 41 along the electrical axis 39 which issubstantially midway of the deflection system 8. The beam 9 then followsdivergent paths until the beam reaches the surface of aperture plate 11.Aperture plate 11 has formed therethrough selecting aperture 12. Theselecting aperture 12 may be positioned substantially coaxially with andsymmetrically'disposed about the electrical axis 39 of the tube. Onlyone of the character shaped beams 15 selected from a plurality ofvarious shaped beams is directed through the aperture 12 at any singleinstant of time. Theshaped beam 15 is therefore projected from theaperture 12 substantially along the electrical axis. After the desiredbeam has been selected, the beam may be directed to any part of theviewing screen or target of the tube by'deflection system 16. Deflectionsystem 16 utilizes preferably the same construction as deflection system8 as aforestated.

Details of the deflection systems 8, 16, 28, 29 and 30, all `of whichmay be identical, are shown in Figure 4. Deflection system 28 of Figure3 is also referred to as the first deflection system. Deflection systems8 of Figuresl and 2 are also known generally as second deflectionsystems. Deflection systems 16 of Figures l and 2 and Vsystem 30V ofFigure 3 are generally known as third deflection systems. Deflectionsystem 29 shown in Figure 3is known as fourth deflection system. InFigure 4, one pair ofV plates 10, may be used to deflect electrons,forexample, in a horizontal direction, and two pair of plates 3, 3 and5, in combination, to deflect electrons-in a vertical direction. Thedeflection sensitivity of the dual or split pair of plates 3, 3 and 5, 5is essentially equivalent to that of the single pair of plates. That is,plates 10, 10 will establish an electrostatic field having apredetermined field density, and each pair of plates 3, 3 0r 5, 5 willestablish a field substantially one half of the predetermined fielddensity. Therefore, part of the beam deflection, vertical in thisexample, is accomplished prior to passage of the beam through thehorizontal plates 10, and a further deflectionof the beam is made afterpassage of the beam through the horizontal plates.

Some of the newly found advantages and results to be gained through theuse of such a system 8 or 16 in the selection of a particular charactershaped beam through the aperture 12 and for a better understanding ofthe operation thereof, examine with reference to Figures 6a, b and c.One of the objectives of this invention is, by means of a system ofdeflection plates 8 or 16, to return an electron beam to a normal axisof an electron optical system such as, referencing accomplished byplates 29, whether the electron beam is approaching the axis from avertical direction, or from a horizontal direction. This basic operationis common to most applications of the system. In Figures 6a, b and c,the path of an electron beam 13 is vshown leaving the plane of thematrix 17 in the direction of the electro-optical or electrical axis 18which is co-axial with the aperture 12 of the aperture plate 11. Acommon deflection plane 21, perpendicular to the optical axis 18, may,for purposes of explanation, be positioned approximately midway betweenthe matrix 17 and the aperture plate 11.

In Figure 6a, a pair of deflection plates 10, 10 is located,electrically, at the central deflection plane 21, and the path of thebeam intersects the axis 18 at the latter plane 21. When the properpotentials are applied to the deflection plates 10, 10 the beam can bemade to follow the axis through the aperture 12. At 6b, a second set ofdeflection plates 23, 23' is shown positioned in a conventional mannerwith respect to the first set 10, and viewed as though they have beenrotated about the axis with respect to the first set. A beam is directedalong a path 13' toward the axis 18 to a point at which the latter isintersec'ted by Athe mid-deflection plane 21. When potentials areapplied to the second set of plates 10, 10 for the purpose of directingthe beam through the aperture 12, th beam 13 will cross the axis 18 atthe plane of the aperture plate 11.

Since it is desirable to have the beam 13' pass through the aperture|and remain on axis, the invention provides the separation of thedeflection surfaces of the respective plates 23 and 23', shown at (b),into substantially equal halves 3, 3 and 5, 5', as shown at (c) having`a capability of generating a field density of one-half that of plates10, 10'. Plates 3, 3' and 5, 5 are positioned on opposite sides of thehorizontal plates 10, 10' orthogonally disposed about the axis withrespect to plates 10, 10 and substantially spaced along the axisequidistant from the deflection plane 21. When the potentials areapplied to the dual pair of plates the first pair 3, 3 will deflect thebeam along -a path 13" which intersects the axis 18 at the deflectionplane 21' of the second pair of plates 5, 5' but the latter plates willreturn lthe beam on the axis and through the aperture 12. Plates 3, 3fand 5, 5' may together furnish electrostatic field density of the sameamount as is furnished by `plates 10, 10. In addition, it is possible tophysically cut in half widthwise one of the plates 10 thereby furnishinga plate 3 which has l/2 the width of plate 10, but the same length. Thiseases manufacture considerably. Such an Aapproach is not however, theonly approach in establishing with each pair of plates 3, y3' and Y5, 5a one-half field density of that generated by plates 1'0, 10.

' With the vdeflection system 8 it is possible to have all selectedbeams pass throughthe electrical center of the final 'deflection system16. ySystem 16 will deflect the from theaxisl tothe desired position onthe screen. therefore be possible to achieve `Vgood registrationffcliaracter images on the screen V40, independently of Where thelcharacters happento appear in the matrix 7. Asshown in Figure 401),plates- 3, and 3', 5 may be structurally joined together and positionedin encompassingA relation to plates 10, The final deflection platesystem 16 of Figure 1 is similar to the aperture selection plate system8, and the advantages to be gained through each system are similar. Ineach case, the effects of deflecting beams in either vertical orhorizontal directions will be as though the bending of the beams istaking place at a common deflection plane. `Improve ments inregistration will thereby result from the establishment of somewhat morerectangular patterns on the viewing screen.

`In Figure 2 anotherembodiment of the invention, utilizing the improveddeflection plate systems, makes use of a cathode emitter 22 ofcharacterV shaped beams. An emitter of this type is similar to thatdescribed in my copending application Serial No. 537,112. Still anotherembodiment of this invention is shown inFigure 3, which makes use of theimproved deection systems in a character beamforming gun similar to thatdescribed in the col pending application Serial No. 507,856.Thedeflection plate systems 28 for the selection of character shapedbeams in these `latter embodiments of the invention may be of the typeto be described in connection with Figure 5. The plate systems shown inFigure 5 contain additional improvements over those described and shownin Figure 4, which are hereinafter described. The plates 3a, 3b, and 5a,5b may be structurally joined together as are the plates of Figure 4,but the cross-section of the plates of Figure 5 is a substantiallyparabolic curvature. The curvatures are symmetrically disposed about theaxis Vin orthogonal and spaced relation to each other.

Reference is now made to Figure 7, which diagram shows, by way ofexample, the source of spherical aberrations normally experienced in theuse of electron lens systems of either the electrostatic or magnetictypes. The effects of spherical aberrations on the registration, oralignment of message characters on the viewing screen of the tube, isexemplified in Figure 8. n

Pincus'hion distortion in the projected matrix pattern of Figure 8 isevidence of spherical aberration. If the matrix heights are mf foraparaxial ray, and m for a marginal ray, there will be a difference,Aq=Az in the focal positions of the two rays. If the focal pointsv wereco-incident the magnification ratio of the projected-image height y tothe matrix height m would be constant, or y/m y/m". However, since thefocal points are not co-incident, the latter ratio will be greater. Fromsimple geometrical considerations, the ratio of marginal to par- 'axialmagnification is given by: (l-l-Aq/x) (l-Aq/2-Z8), for the drawing shownin Figure 7. The resultant matrix shape was obtained with a projectiondistance of x=28 inches.

The present invention aids in minimizing the distortion normal inapparatus such as shown lin Figure 1. The minimization of thedistortions may, in addition, be aided by the proper orientation ofcharacter shaped openings in the matrix. Since a square pattern ofcharacter shaped openings in a matrix 7 are transformed into apincushioned array of images after they have passed through Iaconvergence lens 6, this pincushioning can be overcome by properlocation of the openings in the matrix, or on the surface of the cathode22, which will be somewhat in the form of a barrel. After a barrelledarray of electron images have passed through the lens, the effects oflens Iabberrations will convert the array to a square pattern. Thelatter is desirable since, under these conditions, the application oflineraly stepped signals to the selection plate system 8 will producethe desired selection of character shaped beams through the aperture 12.

'.If a similar approach is-'attempted in the case of Figure genees3tocorrect `for these'spherical aberrations, vthe character selectionplatesystemof Figure 4 would then have to be operated from 'a non-linearselection voltage source. This, ofcourse, is undesirable from thestandpoint of the complications that-would be added tothe circuitry V-inorder to provide'the required character selection signalanonlinearities.However, through the use of the noveldefiection plate system shown inFigure 5, Vit will also be possible to minimizevthe effects of sphericalIaberrations in the convergenceV lens by proper orientationV ofcharacter shaped openings inthe matrix. This improved plate system maybe designed so as torfunctionV ina manner that will Aproduce therequired degree of deflection non-linearity in 'response to linearcontrol signal inputs. f

The degree of pincushioningpor misalignment of the characters in adisplay of the matrix format on the screen of the tube is directlyrelated to the degree of misregistrationHofe-charactersV appearing in adisplayed message. With further reference to Figure 8,V charactershaving the greatest amount of misregistration will be those in thecorners of the matrix, such as, Q, Z, and The other charactersshowing alesserdegree 'o f misregistration would be those assuming the positionsof the characters a t2r, w, etc. A j

The-'layout of squares, IIL in Figure 9 explains further the effect o flens aberrations on character rrlisregistration.44 Each' squarecorresponds to the position of a characteryin the display of a-normallyrectangular format of characters in a matrix as shown, for example, inFigure 9b,j In each ofthe layouts referred to in Figure 9, onlythe upper1/2 ofwa complete layout of characters is shown, and in each case, abovecenter lines C, f

The deflection system of Figure 5 will make it possible to `arrange thecharacters inthe matrix so that curved lines and columns of charactersshown in Figure 9a, will take the form of a square raster instead of onehaving the outlineiof a ipincushion. The first requirement of thisembodiment will be to engrave the openings in the matrix in abarrel-shaped arrangement, as indicated in Figure 9c, in lorder that animage of the matrix format will appear in theform of a square, as shownin Figure 9b, after having passed through the convergence field tothecoil.

The'dellection systems shown in Figures 4 and,v 5 are similar in thatthey both produce the effect of co-planar deflection. i The importancedifference between the two systems, however, may be noted in Figure 4c,and Figure 5c, respectively. The views shown are looking at theends ofthe plates, in the direction of the electron ygun source, Thecross-section of the plates at FigurejeareshownY to have the paraboliccross-section presenting a deflection curvature While that of Figure 4cshows a rectangular cross-section. In operation, if the beam 26 isydeflected upward by plates Sa-Sb, thedegree of movementtoward plate 5bwill be a functionV of beam velocity, distance between plates, andpotential difference applied tothe plates. If a potential is alsoapplied to plates 10a-10b and, for example, deflected in the directionsof plate 10b, the beam deflection in the vertical directionof plate 5bwill decrease. 4Thisvdecreased vertical position of the beam 26 will bein relation to the increased spacing between the deflecting surfaces ofplates 5a and 5b, with respect to beam position, as the beam isdeflected horizontally away from the normal axis of the system.

Since a barrel shaped array of characters, similar to that shown inFigure 9c, can be made inversely proportional to a pincushion image of anormally rectangular matrix format of beams after having passed througha convergence lens, the plates Saz-5b, and 10a-10b, may be shaped sothat linearly applied signals to said plates may cause an electron beamto respond in a particular barrel shaped manner of beam deflection. Toexplain further, with reference to Figures 9a, b and c, a character 19bin the corner of the matrix 2Gb may assume a position 19a on -thescreen, with respect to a properly aligned position 19a',` because ofthe effects of lens aberrations.. If, on

7 the other hand, the eharacterw19cin the matrix `20c was displaced withrespect to amore linear position 1,9,c.,`the effects of lensaberrationswouldallow the character 19e to assume a positionr19a'onrthe screen ofthe tube. v

Figure 3 shows the respective locations of all of the essentialelements, discussed thus far. The electron gun 25 at one endy of displaytube projects the beam of electrons along the axisof thel tube and*Ainto the character selection plate system 2,8. The beam 26 is thendirected through selectedropenings in the matrix 20 and then into themagneticfleld of a convergence lens 6 which, in turn, redirects ,theelectron beam toward the normal axis of the gun at thel deflectionplanev of the reference plates 2,9. After the electron beam is returnedVto the axis of the tube it enters thefield of ,deflection plates 30which positions the beam on the viewingscreen of the tube.

The selection platesZSY may be of 4a construction shown by platesystem'of- Figure 5', and the reference plates 29 may be of the typeshownby thevplate system of Figure 4. The selection `rplates -3ar3bfand5a-5b,.in combination with 10a-10b will convert linearly applied controlvoltages to nonflinear deflections ofthe electron beam Y26. As explainedin connection withFigure 9c, the character openings can be arranged inthe matrix to compensate for the lens aberrations,jand the non-linearityof the arrangement of characters can be compensated for by proper designof the selection plate system 28 with regard to the geometry of the deflecting surfaces.

The'particular embodiments ofthe invention illustrated and described`hereinrarev illustrative only and the invention includes such othermodifications and equivalents as may readily appear to'those skilled inthe art, Within the-scope ofthe appended claims.

Iclaim:

1. nArcathode ray display tube comprising an evacuated envelope, a beamgeneratingmeans placed adjacent one end of-the envelope for vgeneratingand projecting an electron beam substantially along an electrical axis,a target positioned at the other end of the envelope and respondingtovimpingement of the beam thereon, a deflection system for Vdeflectingthe beam, the system being disposed substantially symmetrically aboutthe electrical axis and intermediate the beamgenerating means and thetarget, the deflection system comprising a first set of deflectionplates, and two substantially identical second sets of deflection platesdisposed in substantially orthogonal spaced relation tothe first set,one second set being disposed on either side of thefirst set, the secondsets being structurally joined together.

2. A cathode ray display tube comprising an evacuated envelope, a beamgenerating means placed adjacent one en d of the envelope for generatingand projecting an electron beam substantially along an electrical axis,a target positioned at the other end of the envelope and responding toimpingement of the beam thereon, a deflection system for deflecting thebeam, the system being disposed substantially symmetrically about theelectrical axis `and intermediate the beam generating means and thetarget, the deflection system comprising a first set of deflectionplates, and two substantially identical second sets of deflection platesdisposed in substantially orthogonalgspaced relation to the first set,one second set being disposed on either side of the first set, thesecond sets being structurally joined together and positioned about thefirst set in symmetrically spaced apart relation thereto.

3. A cathode ray display tube comprising an evacuated envelope, a beamgenerating means placed adjacent one end of the envelope for generatingand projecting an electron beam substantially along an electrical axis,a target positioned at the other end of the envelope and responding toimpingement of the beam thereon, a deflection system for deflectingthebeam, the system being disposed substantially symmetrically about theelectrical axis and intermediate the beam generating `means and thetarget, the Adeflection .system comprisingY a first set.of deflectionplates, and two substantially identical second setsjofvde-j ectionplates disposed in substantially orthogonal spaced relation to the firstset, one secondsetbeing disposed on either side of the first set, thesecondsets being strue-A turally joined together, each of theplate'slhavingfasubstantially rectangular crossfsection. y

4. A cathode ray display tube comprising'y an evacuated envelope, a beamgenerating means placed adajacentone end of the envelope for generatingand projecting an electron beam substantiallygalongran electrical axis,a target positioned at the other end of the envelope'and responding toimpingement ofthe beam thereoma deflectionsystem for deflecting thebeam, the system .being disposed substantially symmetrically about thevelectrical. axis and intermediate the beam generating means andj thetarget, the deflection system comprising a first set.ofdeflectionplates, and two substantially identical second-.sets of deflectionplates disposed in substantially orthogonal spaced relation to the firstset, one second set beingdisposed on either side of the first set, thersecond sets being structurally joined together, each of the plateshaving a substantially parabolic cross-section curvature, the platesbeing arranged symmetrically about the axis and having their curvaturespositioned in orthogonal spaced relation to each other.

5. A cathodefray display tube comprisingan evacuated envelope, a beamgenerating meansplaced adjacent one end of the envelope for generatingand projecting an electron beamsubstantially along an electrical axis, atarget positioned at the other .end of the envelope and responding toimpingement of the beam thereon, a deflection system for deflectingthebeamsaid system being capable of effecting deflection ot the beam intwo'predetermined stagesdirecting the beam toward and along the axis,thesystem being disposed intermediate the beam generating means ,and thetarget, the deflection system comprisinga-'first set of deflectionplates,. and two substantiallyidentical second setsof deflection platesdisposed in substantially orthogonal spaced relation to the first set,one1second set beingdisposed on eitherside of the first set.

6. A cathode ray display tube comprising an evacuated envelope, a beamgenerating-tmeans placed adjacent one end ofthe envelope for generatingand projecting an electron beama target-positioned atthe other end ofthe envelope and responding toimpingement of the beam thereon,beamforming means presenting apertures for imparting atleast onevr crosssectional shape to the beam, said apertures being aligned in a barrelshaped array, the beam forming means being positioned intermediate thegenerating means and the target, convergence means positionedintermediate the generating means and the forming means for focusing the,beam to a predetermined location,a second and a third deflection systemfor deflecting the beam, each of thevdeflection systems comprising afirst set of deflection plates, and two substantially identical secondsets of deflection plates disposed in substantially orthogonalspacedYrelation to the'first set, one second set being disposed on either side4of the first set, the second deflection system being positioned atsubstantially the location, an apertured plate having an aperture ispositioned intermediate the location and the target, the thirddeflecting systeml being positioned intermediate the apertured .plateandthe target,--the second deflection system being adapted to causeselective deflection of the beam to directportions thereof through 'theaperture toward the third ldeflecting means, the third deflection systempositioning that portion Vof the beam at a desired location on thetarget,.sraid deflection systems being adapted to cause successivepresentation of said cross sectional shape upon the target inafrectangular array.

7. A cathode ray display tube'comprising anevacuated envelope, a beamgenerating m'eans placed adjacent one end of the envelopeforgeneratingvand projecting an electron beamsubstantially.,alongtan,electrical axis, Aa target positioned at theother end of the envelope and responding to impingement of the beamthereon, a deflection system for deecting the beam, the system beingdisposed substantially symmetrically about the electrical axis andintermediate the beam generating means and the target, the deectionsystem comprising a rst set of deection plates, and two substantiallyidentical second sets of dellection plates disposed in substantiallyorthogonal spaced relation to the first set, one second set beingdisposed on either side of the lirst set, each of said second sets beingstructurally joined together, a linearly graduated voltage source forapplication to the dellection system, said system responding to thelinear voltage with a non-linear response.

8. A cathode ray display tube comprising an evacuated envelope, a beamgenerating means placed adjacent one end of the envelope for generatingand projecting an electron beam substantially alongran electrical axis,a target positioned at the other end of the envelope and responding toimpingement of the beam thereon, a deflection system for dellecting thebeam, the system being disposed intermediate the beam generating meansand the target, the deflection system comprising a first set ofdeflection plates having a predetermined surface area, and twosubstantially identical second sets of deection plates disposed insubstantially orthogonal spaced relation to the lirst set, one secondset being disposed on either side of the rst set, the plates of thesecond sets having a surface area of one-half the predetermined surfacearea, the second sets being equally spaced from the rst set and theIirst set and second set being equally spaced from and symmetricallydisposed about the axis.

9. A cathode ray display tube comprising an evacuated envelope, a beamgenerating means placed adjacent one end of the envelope for generatingand projecting an electron beam substantially along an electrical axis,a target positioned at the other end of the envelope and responding toimpingement of the beam thereon, a deflection system for deecting thebeam, the system being disposed intermediate the beam generating meansand the target, the deection system comprising a first set of deectionplates, and two substantially identical second sets of deection platesdisposed in substantially orthogonal spaced relation to the first set,one second set being disposed on either side of the first set, each ofsaid second sets being structurally joined together, the irst and secondsets interactng with the beam and being adapted to effect upon the beamcross section a correction of pincushion and barrel distortion in thetube. v

10. A cathode ray display tube comprising an evacuated envelope, a beamgenerating means placed adjacent one end of the envelope for generatingand projecting an electron beam substantially along an electrical axis,a target positioned at the other end ofthe container and responding toimpingement of the beam thereon, a deflection system for deecting thebeam, the system being disposed substantially symmetrically about theelectrical axis and intermediate the beam generating means and thetarget, the deflection system comprising a first set of deflectionplates, and two substantially identical second sets of deection platesdisposed in substantially orthogonal spaced relation to the irst set,one second set being disposed on either side of the first set, thesecond sets being structurally joined together, a linearly graduatedvoltage, the deflection system being responsive to the voltage to etectcoplanar-like selectively horizontal and vertical deections of the beamwith substantially complete beam angle deflection response.

References Cited in the le of this patent UNITED STATES PATENTS2,302,786 McGee Nov. 24, 1942 2,574,975 Kallmann Nov. 13, 1951 2,617,078Van Overbeek Nov. 4, 1952 2,623,167 Diemer Dec. 23, 1952 2,711,493Lawrence June 21, 1955 .2,728,872 Smith Dec. 27, 1955 2,728,873 McNaneya Dec. 27, 1955

